The dream of telescopic magnification is perhaps as old as mankind itself. Already Roger Bacon (c. 1219 - c. 1292) had dreamed of a device with which "a child might appear a giant, and a man a mountain". But why then was it not until 1608 that a spectacles-maker of Middelburg applied for an exclusive patent for a device that enlarged distant objects? What laid between the dream and reality? The search for an answer to these questions passes through the stages of developing an optical theory and producing lenses in the two centuries prior to the invention of the telescope.

Optics was a well-established mathematical discipline, boasting a tradition rooted in Antiquity. In the Middle Ages it became known as "perspectiva", and the perspectivist tradition of optics served as basis for many mathematicians who tried to establish the properties of mirrors and lenses in the 16 th century. But the conceptual innovations emerging from studies in the perspectivist tradition of optics soon came up against the material limitations imposed by the artisans’ crude methods of constructing lenses.